Why Yards Flood in Amarillo

Amarillo's drainage problems are older than its paved streets. The town took its name from a playa called Amarillo, or Wild Horse, Lake, and its first townsite was platted on a section of land containing that playa -- ground a rival promoter warned would flood in rainstorms. In the spring of 1889 heavy rains nearly flooded that "Old Town" -- a railroad embankment kept the water from draining off -- and more people moved to Henry Sanborn's higher townsite; most of the town had relocated by 1890. Your yard is dealing with the same forces those settlers were: tight clay, closed basins, a hard layer of lime underneath and storms that arrive all at once.

The clay under the lawn

The soil most associated with this part of the Panhandle is Pullman clay loam. The USDA first described the series in Potter County in 1929, lists it as a benchmark soil of large extent on the Southern High Plains, and placed its reference profile in a field north of Hereford. Its official description calls Pullman slowly permeable. Below a thin topsoil, the subsoil horizons carry 35 to 50 percent clay, and the profile is rated as having vertic properties: it expands as it takes on water, contracts as it dries, and opens cracks that run deep into the subsoil.

Two things follow for a homeowner. First, rain soaks in at the clay's pace, not the storm's pace, so in a heavy downpour most of the water has to go sideways across the surface. Second, the same clay moves. A yard that stays soggy along one side of the house and bone-dry along the other puts uneven moisture against the slab, which is why drainage and foundation worries tend to show up together here.

One honest caveat: the soil survey rates Pullman itself as well drained, meaning it doesn't stay waterlogged for long under normal conditions. The trouble is the rate. Water that can't get into the ground fast enough piles up wherever the surface sends it, and on a nearly level lot that can be one corner of your backyard.

The playas the city was built around

Playas are shallow basins scattered across the southern High Plains. The Handbook of Texas estimates about 19,000 in the Texas portion alone, averaging near 600 per county, and notes that no stream feeds or drains them: each one collects runoff from its own small, closed watershed. The basin is often lined with Randall clay, which the USDA describes as poorly drained, very slowly permeable and frequently ponded for very long periods. Playas with Randall soils sit roughly 10 to 50 feet below the surrounding plain.

Amarillo didn't fill its playas in -- it put them to work. The City of Amarillo's Drainage Utility maintains several city-owned playa lakes that are used to store stormwater runoff, runs pump stations that remove stormwater from low-lying areas, and publishes live level, rainfall and camera data for eight of them, including Lawrence, McDonald, T-Anchor and Willow Grove lakes. The city's stormwater program also notes that runoff from inside city limits is unlikely to reach the Red River and may only intermittently reach the Canadian. In plain terms, a lot of Amarillo's storm water has no river to run to, so it heads for the nearest low spot.

If your lot sits on the slope between a street and a playa, some of that traffic passes through your yard. That's why two houses on the same block can have completely different drainage problems.

The caliche below the clay

Dig deep enough under Pullman soil and the color changes. The soil survey places the first secondary carbonates -- lime that has built up within the soil -- about 20 to 30 inches down, and a calcic horizon about 30 to 60 inches down, where calcium carbonate can make up a large share of the soil. That chalky, nodular layer is the start of what most people here call caliche.

In some spots it hardens into rock. The Handbook of Texas calls the Caprock a hardpan that formed a few feet below the ground when mineral-rich subsoil cemented itself into a rock-like layer. The USDA describes soils such as the Kimberson series, typically found on plains next to escarpments, where indurated platy caliche starts as little as 4 to 20 inches below the surface and is very slowly permeable. Lots near draws, the Canadian River breaks or the Palo Duro Canyon country in Randall County deserve a probe before anyone commits to a trench depth. Either way, water that reaches the lime zone tends to slow down or move sideways rather than keep sinking.

The storms that bring the year's rain

NWS Amarillo puts the 1991-2020 normal at 19.66 inches a year. The calendar matters more than the total: roughly 12.5 of those inches, about 64 percent, fall from May through September, with June, July and August each averaging close to 3 inches. January and February together average about an inch and a quarter. The weather service's Panhandle climate guide adds that 93 percent of hail events in the region occur between May and September -- the same months that carry most of the rainfall total.

Storms here can be extreme. Amarillo's records include 3.36 inches in a single hour on June 24, 1948, and 5.74 inches in one calendar day on July 7, 2010. You don't need a record storm to flood a yard, though. A one-inch burst in half an hour is plenty when the clay underneath takes it in slowly.

What it means for a fix

Put those pieces together and a few rules fall out:

• Plan the exit first. Slow clay and a lime layer below it mean a drain should carry water to a discharge point, not count on the ground to absorb it.
• Size for summer, not the annual total. Pipe and inlets need to handle a short, heavy storm, because that's when the problems happen.
• Read the slope toward the nearest basin. Some of your water may start two lots uphill, and an interceptor drain at the property line can beat a drain around the puddle.
• Expect the dig to change. Hitting caliche can change trench depth and routing, so we probe before we commit to a layout.
• Keep the slab's moisture even. Grading and downspout extensions that move roof water away from the foundation are often the cheapest part of the job and among the most useful.

Where the lot has no downhill at all, a sump that lifts water to an approved discharge is usually the dependable choice. More on the options is on our French drain and sump pump pages.

Signs to watch

• Water still standing two or more days after a storm.
• Wide cracks opening in the yard during dry months, especially near the house.
• A strip of lawn that stays dark, soft or mossy.
• Silt fans on a sidewalk or patio where runoff crosses.
• Doors that stick after a wet spell and loosen after a dry one.

Any of these is a good reason to request a free on-site assessment. We'll walk the lot, find where the water starts and where it stops, and tell you plainly whether it needs a fix now or can wait.